The program will generate all permutations of the input string.

string_permutations.c

// Created by: Thomas Hewton-Waters
// Date: February 18, 2012

/* The program will generate all permutations of the input string. */

#include <stdio.h>
#include <string.h>

void merge( char end, char str[], char perms[][100] );
void permutate( char str[], int index, int *num_perms );

int main()
{
	char str[105];
	int x, *num_perms;
	num_perms = &x;
	*num_perms = 0;

	printf( "Please enter letters to be permutated: " );
	scanf( "%100s", str );
	printf( "Permutating %s", str );

	permutate( str, 0, num_perms );

	printf( "Total number of permutations: %d\n", *num_perms );
}

void permutate( char str[], int index, int *num_perms )
{
	int i = 0;
	char temp;

	if( index == strlen(str) - 1 ) {
		(*num_perms)++;
		printf( "%s\n", str);
		return;
	}

	for( i = index; i < strlen(str); i++ ) {
		temp = str[i];
		str[i] = str[index];
		str[index] = temp;

		permutate( str, index + 1, num_perms );

		temp = str[i];
		str[i] = str[index];
		str[index] = temp;
	}
}